An experimental approach for the utilization of tannery sludge-derived Bacillus strain for biosorptive removal of Cr(VI)-contaminated wastewater.

Biosorption efficacy of Bacillus strain DPAML065, isolated from the tannery sludge, was appraised for the removal of toxic hexavalent chromium (VI) ions from synthetic wastewater. Effects of the process variable on biosorbent surface by variation in pH, metal Cr(VI) concentration and retention time were examined using batch experiments. The isolated Bacillus strain biosorbent was studied for its morphology and surface chemistry through FE-SEM, EDX and FTIR. It discloses that, the reduction mechanism of Cr(VI) during the process is mainly attributed to precipitation in addition to the functional groups (such as -COOH, -OH, C-O, P=O) present on the cellular matrix of Bacillus. Biochemical tests and 16s rRNA sequencing were also performed to identify the biosorbent at the genus level. A 95% Cr(VI) removal efficiency was procured by Bacillus strain DPAML065 biosorbent at pH 6, incubation period 24 h, 80 mg/L initial feed concentration and operational temperature 35 °C. Equilibrium behaviour of chromium binding follows the Langmuir isotherm model (R = 0.968) with an adsorption capacity of 106.38 mg/g. Kinetic modelling disseminates that biosorption of Cr(VI) ions by Bacillus strain DPAML065 obeyed pseudo-second-order model (R = 0.984) rather than the pseudo-first-order model. Concisely, the results indicate that the Bacillus strain DPAML065 is a potential, economically feasible and eco-friendly biosorbent which can be effectively used for removal of chromium (VI) from wastewater.